Entrenamiento muscular inspiratorio (Evaluación): ¿Cómo obtener más beneficios?

en Inglés

Entrenamiento muscular inspiratorio para el rendimiento deportivo, asma, EPOC, fibrosis quística y otras condiciones

Hombres remendo

La mayoría, aunque no todos, de los ensayos clínicos han encontrado beneficios de entrenamiento muscular inspiratorio en el rendimiento deportivo de los remeros (Volianitis et al, 2001; Klusiewicz et al, 2008; Riganas et al, 2008), los ciclistas (Romer et al, 2002a; Romer et al, 2002b), y los nadadores (Kilding et al, 2010; Wells et al, 2005; Mickleborough et al, 2008).

Los ensayos clínicos también probaron los efectos del entrenamiento muscular inspiratorio en el asma, EPOC, bronquiectasias, fibrosis quística, diabetes, antes y después de la cirugía, la insuficiencia cardíaca crónica, cardiopatía isquémica, accidente cerebrovascular, el destete del ventilador, y las enfermedades neuromusculares (se proporcionan algunas referencias con las conclusiones a continuación).

Oxígeno en cerebro

La mayoría de estos estudios han demostrado los siguientes beneficios:
– Reducción de la disnea (sensación de falta de aire) durante el ejercicio en los atletas y en reposo o durante el ejercicio muy ligero en los pacientes
– Aumento de la fuerza de los músculos inspiratorios durante la práctica de ejercicio intenso para los atletas
– Aumento de la resistencia en pacientes con mejoras en algunos parámetros de la función pulmonar
– Reducción de la medicación y la mejora de la calidad de vida en las personas con enfermedades crónicas.

Hombre atleta nadando

La mayoría de estos estudios han utilizado los siguientes entrenadores respiratorios o dispositivos: Ultrabreathe, Powerlung, Powerbreathe, y Expand-A-Lung.

El objetivo señalado del entrenamiento de los músculos respiratorios y de inspiración es mejorar el transporte de oxígeno. Vamos a considerar los problemas con el transporte de oxígeno a las personas enfermas con disnea (falta de aire) en reposo.

La disnea y el transporte de oxígeno

La disnea en los pacientes, y en cierto grado en los atletas de competencia o entrenamiento es casi siempre acompañados por el transporte de oxígeno ineficiente e hipoxia tisular resultante. Mientras que el entrenamiento muscular inspiratorio se centra en los efectos mecánicos, nos vamos a centrar en los efectos celulares relacionados con el mecanismo de transporte de oxígeno.

Hombre con dolor en el pecho

Las personas con enfermedades del corazón, asma, diabetes, EPOC, y muchas otras condiciones, tienen ventilación minuto en reposo enormemente elevada: cerca de 2-3 veces más que la norma médica. (La norma es de 6 L/min para un hombre de 70 kg.) Esto ha sido conocido por los médicos clínicos durante décadas y probado por decenas de estudios. ¿Cuáles son los efectos?

La hiperventilación crónica, (y aquí tenemos evidencia de apoyo aún más impresionante), provoca la hipoxia celular sistémica. El mecanismo de transporte ineficiente O2 y la hipoxia tisular resultante depende de la presencia de problemas pulmonares (desajuste ventilación-perfusión). Para los pacientes con pulmones normales (por ejemplo, la mayoría de las personas con enfermedades del corazón y diabetes), la hiperventilación alveolar lleva a hipocapnia arterial (falta de CO2 en la sangre arterial). Dado que el CO2 es un potente vasodilatador, la hipocapnia conduce a la constricción de las arterias y arteriolas que causan la perfusión reducida y a un aumento de la resistencia al flujo sanguíneo sistémico.

Médicos

Además, la falta de CO2 en los tejidos suprime el efecto Bohr causando reducción de la liberación de oxígeno en las células. Estos dos efectos reducen significativamente el suministro sistémico de oxígeno (Laffey y Kavanagh, 2002; Nunn, 1987). Hay, sin embargo, algunas diferencias en la reducción del suministro de oxígeno a los distintos tejidos musculares. La disminución de la oxigenación del músculo del corazón debido a la hiperventilación hipocápnica está bien documentada (Foex et al, 1979; Karlsson et al, 1994; Okazaki et al, 1991; Okazaki et al, 1992; Wexels et al, 1985). Del mismo modo, una gran reducción en la presión parcial de O2 se lleva a cabo en los músculos lisos de los dos puntos (Guzman et al, 1999), con una disminución más moderada de los músculos estriados esqueléticos y (Gustafsson et al, 1993; Thorborg et al, 1998; Okazaki et al, 1989). Resultados de la hipoxia tisular en la respiración celular anaeróbica en reposo y los niveles de ácido láctico en la sangre elevados (común para todas estas condiciones de salud). Estos efectos agudizan la sensación de fatiga en los músculos respiratorios (experimentado una dificultad para respirar) en reposo en los pacientes y durante el ejercicio en los atletas.

Dióxido de carbono

Por otra parte, ya que el dióxido de carbono es un fuerte dilatador de las vías respiratorias (ver enlaces a estudios más abajo), la broncoconstricción hipocápnica aumenta la resistencia de la vía aérea. Además, la hipoxia celular provoca la generación de radicales libres, la supresión del sistema inmune, y favorece la inflamación crónica. Por lo tanto, las infecciones frecuentes, la inflamación de las vías respiratorias y la producción de mucosidad adicional pueden empeorar drásticamente el síntoma de disnea.

Por lo tanto, la disnea es causada por factores que todos se originan en la hiperventilación crónica en reposo.

Gráfico de dificultad de respiración

Efectos de la hiperventilación en el transporte de oxígeno durante el ejercicio

Durante el ejercicio físico, si los niveles de CO2 alveolar caen (la hiperventilación en relación con la producción de CO2), los principales efectos en el transporte de oxígeno son los mismos: menos oxígeno se suministra a los tejidos debido a la vasoconstricción hipocápnica y la supresión del efecto Bohr.

Conclusiones

La formación de los músculos inspiratorios puede ser un objetivo independiente para los ejercicios de respiración. Sin embargo, este tipo de entrenamiento (mejora de la fuerza de los músculos inspiratorios) no aborda el mecanismo de transporte reducido de oxígeno durante la disnea (falta de aliento o dificultad para respirar). Por lo tanto, el principal potencial fisiológico y en beneficio del entrenamiento de respiración se mejora los patrones de respiración, VO2máx y resultados de pruebas de oxigenación del cuerpo en reposo (respiración más lenta y más ligera con la frecuencia respiratoria reducida y la tasa de ventilación por minuto). Todos estos efectos se pueden alcanzar con exhalaciones más largas durante el entrenamiento de los músculos inspiratorios. Las correcciones de estilo de vida (ver sección de aprendizaje aquí) mejorarán los beneficios del entrenamiento muscular inspiratorio también. Los mejores efectos en el rendimiento deportivo fueron ahora encontrados después de la aplicación del dispositivo de respiración cuyo nombre se proporciona justo debajo de aquí como su contenido extra.

Este vídeo de YouTube se explica cómo elegir técnicas de respiración eficaces para niveles altos de oxígeno del cuerpo.

Para las referencias más completas y los resúmenes, ver estudios de entrenamiento muscular inspiratorio.


References

Sports Performance
Riganas CS, Vrabas IS, Christoulas K, Mandroukas K.
Specific inspiratory muscle training does not improve performance or VO2max levels in well trained rowers.
J Sports Med Phys Fitness. 2008 Sep;48(3):285-92.
Ergophysiology Laboratory, Department of Physical Education and Sports Sciences, Thessaloniki, Greece.
… CONCLUSION: In conclusion, six weeks of IMT increases inspiratory muscle strength by approximately 28% in highly trained rowers. However, this increase in inspiratory muscle strength does not appear to improve VO2max, dyspnea sensation during exercise, or rowing performance in well-trained rowers.

Klusiewicz A, Borkowski L, Zdanowicz R, Boros P, Wesołowski S.
The inspiratory muscle training in elite rowers.
J Sports Med Phys Fitness. 2008 Sep;48(3):279-84.
Department of Physiology, Institute of Sport, Warsaw, Poland.
… CONCLUSION: The data obtained corroborate the observations that in well-trained athletes the introduction of the principle of incremental inspiratory resistance allows to improve methodically the inspiratory muscles’ strength. Once the essential period of IMT has been completed, the training volume should be reduced in order to secure the attained level of the inspiratory muscles’ strength.

Volianitis S, McConnell AK, Koutedakis Y, McNaughton L, Backx K, Jones DA.
Inspiratory muscle training improves rowing performance.
Med Sci Sports Exerc. 2001 May;33(5):803-9.
School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
… CONCLUSIONS: IMT improves rowing performance on the 6-min all-out effort and the 5000-m trial.

Romer LM, McConnell AK, Jones DA.
Inspiratory muscle fatigue in trained cyclists: effects of inspiratory muscle training.
Med Sci Sports Exerc. 2002 May;34(5):785-92.
Sports Medicine and Human Performance Unit, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, UK.
… CONCLUSION: These data support existing evidence that there is significant global inspiratory muscle fatigue after sustained heavy endurance exercise. Furthermore, the present study provides new evidence that performance enhancements observed after IMT are accompanied by a decrease in inspiratory muscle fatigue.

Romer LM, McConnell AK, Jones DA.
Effects of inspiratory muscle training on time-trial performance in trained cyclists.
J Sports Sci. 2002 Jul;20(7):547-62.
The Human Performance Laboratory, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, UK.
… These results support evidence that specific inspiratory muscle training attenuates the perceptual response to maximal incremental exercise. Furthermore, they provide evidence of performance enhancements in competitive cyclists after inspiratory muscle training.

Kilding AE, Brown S, McConnell AK.
Inspiratory muscle training improves 100 and 200 m swimming performance.
Eur J Appl Physiol. 2010 Feb;108(3):505-11. Epub 2009 Oct 16.
School of Sport and Recreation, Faculty of Health and Environmental Sciences, AUT University, Auckland, New Zealand.
… In conclusion, 6 weeks of IMT [inspiratory muscle training] has a small positive effect on swimming performance in club-level trained swimmers in events shorter than 400 m.

Wells GD, Plyley M, Thomas S, Goodman L, Duffin J.
Effects of concurrent inspiratory and expiratory muscle training on respiratory and exercise performance in competitive swimmers.
Eur J Appl Physiol. 2005 Aug;94(5-6):527-40. Epub 2005 Jun 8.
Graduate Department of Exercise Sciences, University of Toronto, Toronto, Canada. greg.wells@sickkids.ca
… We concluded that although swim training results in attenuation of the ventilatory response to hypercapnia and in improvements in pulmonary function and sustainable breathing power, supplemental respiratory muscle training has no additional effect except on dynamic pulmonary function variables.

Mickleborough TD, Stager JM, Chatham K, Lindley MR, Ionescu AA.
Pulmonary adaptations to swim and inspiratory muscle training.
Eur J Appl Physiol. 2008 Aug;103(6):635-46. Epub 2008 May 14.
Human Performance Laboratory, Department of Kinesiology, Indiana University, Bloomington, IN 47405, USA. tmickleb@indiana.edu
… This study has demonstrated that there are no appreciable differences in terms of respiratory changes between elite swimmers undergoing a competitive ST program and those undergoing respiratory muscle training using the flow-resistive IMT device employed in the present study; as yet, the causal mechanisms involved are undefined.

Asthma
Ram FS, Wellington SR, Barnes NC.
Inspiratory muscle training for asthma.
Cochrane Database Syst Rev. 2003;(4):CD003792.
National Collaborating Centre for Women’s and Children’s Health, Royal College of Obstetricians and Gynaecologists, 27, Sussex Place, Regent’s Park, London, UK, NW1 4RG.
… REVIEWER’S CONCLUSIONS: Currently there is insufficient evidence to suggest that inspiratory muscle training provides any clinical benefit to patients with asthma. Due to the limited availability of studies in this area there is a need for further trials evaluating the efficacy of inspiratory muscle training devices in patients with asthma. These studies should investigate asthmatics with a range of severity. They should investigate clinically relevant outcomes such as lung function, symptoms, exacerbation rate and concomitant medications.

Weiner P, Magadle R, Massarwa F, Beckerman M, Berar-Yanay N.
Influence of gender and inspiratory muscle training on the perception of dyspnea in patients with asthma.
Chest. 2002 Jul;122(1):197-201.
Department of Medicine A, Hillel Yaffe, Medical Center, Hadera, Israel.
… CONCLUSIONS: POD [perception of dyspnea] and mean daily beta(2)-agonist consumption in asthmatic women are significantly higher, and the P(Imax) significantly lower, than that of their male counterparts. When the P(Imax) of female subjects following training is equal to that in male subjects, the differences in POD and mean daily beta(2)-agonist consumption disappear.

Weiner P, Berar-Yanay N, Davidovich A, Magadle R, Weiner M.
Specific inspiratory muscle training in patients with mild asthma with high consumption of inhaled beta(2)-agonists.
Chest. 2000 Mar;117(3):722-7.
Department of Medicine A, Hillel-Yaffe Medical Center, Hadera, Israel.
CONCLUSIONS: We have shown that patients with mild asthma, who have a high beta(2)-agonist consumption, have a higher perception of dyspnea than those with normal consumption. In addition, SIMT [specific inspiratory muscle training] was associated with a decrease in perception of dyspnea and a decrease in beta(2)-agonist consumption.

Weiner P, Azgad Y, Ganam R, Weiner M.
Inspiratory muscle training in patients with bronchial asthma.
Chest. 1992 Nov;102(5):1357-61.
Department of Medicine A, Hillel-Yaffe Medical Center, Hadera, Israel.
… We conclude that SIMT [specific inspiratory muscle training], for six months, improves the inspiratory muscle strength and endurance, and results in improvement in asthma symptoms, hospitalizations for asthma, emergency department contact, absence from school or work, and medication consumption in patients with asthma.

Asthma – Children
Lima EV, Lima WL, Nobre A, dos Santos AM, Brito LM, Costa Mdo R.
Inspiratory muscle training and respiratory exercises in children with asthma
J Bras Pneumol. 2008 Aug;34(8):552-8.
Faculdade Santa Terezinha – CEST, Santa Terezinha College – São Luís, Brazil.
… CONCLUSIONS: Programs involving IMT [inspiratory muscle training] and respiratory exercises can increase mechanical efficiency of the respiratory muscles, as well as improving PEF and severity variables.

Asthma and COPD
McConnell AK.
The role of inspiratory muscle function and training in the genesis of dyspnoea in asthma and COPD.
Prim Care Respir J. 2005 Aug;14(4):186-94. Epub 2005 Jun 27.
Sport Sciences Department, Brunel University, Uxbridge, Middlesex UB8 3PH, UK.
… IMT [inspiratory muscle training] offers a relatively accessible non-pharmacological treatment for dyspnoea that also improves exercise tolerance and quality of life.

COPD
Decramer M.
Response of the respiratory muscles to rehabilitation in COPD.
J Appl Physiol. 2009 Sep;107(3):971-6. Epub 2009 Apr 2.
Respiratory Division, University Hospital, University of Leuven, 3000 Leuven, Belgium.
Abstract
Respiratory rehabilitation is known to improve outcomes in patients with chronic obstructive pulmonary disease (COPD)… The final question is whether improvements in inspiratory muscle function produced by IMT [inspiratory muscle training] lead to improved outcomes in COPD. In all five studies in which training load was adequately controlled, a significant reduction of dyspnea during activities of daily living was found. Eight randomized studies examined the effects of the combination. Greater improvements in exercise capacity were only found in three studies, and none showed a greater reduction in dyspnea.

O’Brien K, Geddes EL, Reid WD, Brooks D, Crowe J.
Inspiratory muscle training compared with other rehabilitation interventions in chronic obstructive pulmonary disease: a systematic review update.
J Cardiopulm Rehabil Prev. 2008 Mar-Apr;28(2):128-41.
Department of Physical Therapy, University of Toronto, Toronto, Ontario, Canada.
… CONCLUSIONS: Performing a combination of IMT [inspiratory muscle training] plus exercise may lead to significant improvements in inspiratory muscle strength and one outcome of exercise tolerance for individuals with COPD.

Geddes EL, O’Brien K, Reid WD, Brooks D, Crowe J.
Inspiratory muscle training in adults with chronic obstructive pulmonary disease: an update of a systematic review.
Respir Med. 2008 Dec;102(12):1715-29. Epub 2008 Aug 15.
School of Rehabilitation Science, Institute of Applied Health Science, Room 403, McMaster University, 1400 Main Street West, Hamilton, ON, Canada L8S 1C7.
… Results suggest that targeted, threshold or normocapneic hyperventilation IMT [inspiratory muscle training] significantly increases inspiratory muscle strength and endurance, improves outcomes of exercise capacity and one measure of quality of life, and decreases dyspnea for adults with stable COPD.

Crowe J, Reid WD, Geddes EL, O’Brien K, Brooks D.
Inspiratory muscle training compared with other rehabilitation interventions in adults with chronic obstructive pulmonary disease: a systematic literature review and meta-analysis.
COPD. 2005 Sep;2(3):319-29.
School of Rehabilitation Science, IAHS-Room 403, McMaster University, 1400 Main Street West, Hamilton, Ontario, Canada.
The purpose of this systematic review was to determine the effect of inspiratory muscle training (IMT) (alone or combined with exercise and/or pulmonary rehabilitation) compared to other rehabilitation interventions such as: exercise, education, other breathing techniques or exercise and/or pulmonary rehabilitation among adults with chronic obstructive pulmonary disease (COPD)… IMT results in improved inspiratory muscle strength and endurance compared to education. Further trials are required to investigate the effect of IMT (or combined IMT) compared to other rehabilitation inventions for outcomes such as dyspnea, exercise tolerance, and quality of life.

Hill K, Jenkins SC, Philippe DL, Cecins N, Shepherd KL, Green DJ, Hillman DR, Eastwood PR.
High-intensity inspiratory muscle training in COPD.
Eur Respir J. 2006 Jun;27(6):1119-28.
Dept of Pulmonary Physiology, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, Western Australia, 6009 Australia.
… In conclusion, high-intensity inspiratory muscle training improves inspiratory muscle function in subjects with moderate-to-severe chronic obstructive pulmonary disease, yielding meaningful reductions in dyspnoea and fatigue.

Larson JL, Covey MK, Wirtz SE, Berry JK, Alex CG, Langbein WE, Edwards L.
Cycle ergometer and inspiratory muscle training in chronic obstructive pulmonary disease.
Am J Respir Crit Care Med. 1999 Aug;160(2):500-7.
University of Illinois at Chicago, Chicago, Illinois, USA.

Sánchez Riera H, Montemayor Rubio T, Ortega Ruiz F, Cejudo Ramos P, Del Castillo Otero D, Elias Hernandez T, Castillo Gomez J.
Inspiratory muscle training in patients with COPD: effect on dyspnea, exercise performance, and quality of life.
Chest. 2001 Sep;120(3):748-56.
Pneumology Service, Virgen Del Rocio University Hospital, Sevilla, Spain.
… CONCLUSIONS: We conclude that targeted IMT [inspiratory muscle training] relieves dyspnea, increases the capacity to walk, and improves HRQL [health-related quality of life] in COPD patients.

Lisboa C, Villafranca C, Leiva A, Cruz E, Pertuzé J, Borzone G.
Inspiratory muscle training in chronic airflow limitation: effect on exercise performance.
Eur Respir J. 1997 Mar;10(3):537-42.
Department of Respiratory Diseases, Catholic University of Chile, Santiago.
… We conclude that inspiratory muscle training using a load of 30% peak maximal inspiratory pressure, improves dyspnoea, increases walking capacity and reduces the metabolic cost of exercise.

Hill K, Jenkins SC, Philippe DL, Shepherd KL, Hillman DR, Eastwood PR.
Comparison of incremental and constant load tests of inspiratory muscle endurance in COPD.
Eur Respir J. 2007 Sep;30(3):479-86. Epub 2007 May 15.
Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, Western Australia, Australia 6009.
… When assessing inspiratory muscle function in chronic obstructive pulmonary disease via tests in which the pattern of breathing is unconstrained, the current authors recommend incremental load tests be used in preference to constant load tests. However, to attribute changes in these tests to improvements in inspiratory muscle endurance, breathing pattern should be controlled.

Garrod R, Lasserson T.
Role of physiotherapy in the management of chronic lung diseases: an overview of systematic reviews.
Respir Med. 2007 Dec;101(12):2429-36. Epub 2007 Sep 17.
School of Physiotherapy, St. George’s, University of London, Faculty of Health and Social Care Sciences, Cranmer Terrace, London SW17 0RE, UK.

Others than COPD (asthma, bronchiectasis, cystic fibrosis, pre- and postsurgery, ventilator weaning, neuromuscular diseases, and chronic heart failure)
Padula CA, Yeaw E.
Inspiratory muscle training: integrative review of use in conditions other than COPD.
Res Theory Nurs Pract. 2007;21(2):98-118.
University of Rhode Island, College of Nursing, Kingston 02881, USA.
Inspiratory muscle training (IM training) is a technique that is designed to improve the performance of the respiratory muscles (RMs) that may be impaired in a variety of conditions. Interest in IM training has expanded over the past two decades, and IM training has been used in an increasingly wide range of clinical conditions. However, the benefits of IM training continue to be debated, primarily because of methodological limitations of studies conducted to date. The focus of this article is to provide a critical review of IM training research in conditions other than chronic obstructive pulmonary disease for which it has been used, including asthma, bronchiectasis, cystic fibrosis, pre- and postsurgery, ventilator weaning, neuromuscular diseases, and chronic heart failure. Emphasis is placed on what has been learned, remaining questions, future applications, and significance to practice.

Heart Disease
Laoutaris I, Dritsas A, Brown MD, Manginas A, Alivizatos PA, Cokkinos DV.
Inspiratory muscle training using an incremental endurance test alleviates dyspnea and improves functional status in patients with chronic heart failure.
Eur J Cardiovasc Prev Rehabil. 2004 Dec;11(6):489-96.
Onassis Cardiac Surgery Centre, Athens, Greece.
CONCLUSION: Inspiratory muscle training using an incremental endurance test, successfully increases both inspiratory strength and endurance, alleviates dyspnea and improves functional status in CHF [chronic heart failure].

Stein R, Chiappa GR, Güths H, Dallʼago P, Ribeiro JP.
Inspiratory Muscle Training Improves Oxygen Uptake Efficiency Slope in Patients With Chronic Heart Failure.
J Cardiopulm Rehabil Prev. 2009 Sep 22. [Epub ahead of print]
Exercise Pathophysiology Research Laboratory and Cardiology Division, Hospital de Clinicas de Porto Alegre (Drs Stein, Chiappa, and Ribeiro), School of Physical Therapy, UNILASALLE, Canoas (Mr Güths and Dr Dall’Ago), Department of Physiological Sciences, Fundação Faculdade Federal de Ciências Médicas de Porto Alegre, Porto Alegre (Dr Dall’Ago), and Department of Medicine, Federal University of Rio Grande do Sul, Porto Alegre (Dr Ribeiro), Brazil.
… CONCLUSION: In CHF patients with IMW [inspiratory muscle weakness], IMT [inspiratory muscle training] results in a significant increase in OUES [oxygen uptake efficiency slope].

Sutbeyaz ST, Koseoglu F, Inan L, Coskun O.
Respiratory muscle training improves cardiopulmonary function and exercise tolerance in subjects with subacute stroke: a randomized controlled trial.
Clin Rehabil. 2010 Mar;24(3):240-50. Epub 2010 Feb 15.
Fourth Physical Medicine & Rehabilitation Clinic, Ankara Physical Medicine and Rehabilitation Education and Research Hospital, Ankara, Turkey.
… CONCLUSIONS: Significant short-term effects of the respiratory muscle training programme on respiratory muscle function, exercise capacity and quality of life were recorded in this study.

Darnley GM, Gray AC, McClure SJ, Neary P, Petrie M, McMurray JJ, MacFarlane NG.
Effects of resistive breathing on exercise capacity and diaphragm function in patients with ischaemic heart disease.
Eur J Heart Fail. 1999 Aug;1(3):297-300.
Institute of Biomedical and Life Sciences, Glasgow University, Scotland, UK.
… Independent of the mechanisms involved, this small, uncontrolled study suggests that inspiratory muscle training may improve exercise capacity, diaphragm function and symptoms of breathlessness in patients with chronic coronary artery disease even in the absence of heart failure.

Dall’Ago P, Chiappa GR, Guths H, Stein R, Ribeiro JP.
Inspiratory muscle training in patients with heart failure and inspiratory muscle weakness: a randomized trial.
J Am Coll Cardiol. 2006 Feb 21;47(4):757-63. Epub 2006 Jan 26.
Department of Physiological Sciences, Fundação Faculdade Federal de Ciências Médicas de Porto Alegre, Porto Alegre, Brazil.
… CONCLUSIONS: In patients with CHF and inspiratory muscle weakness, IMT [inspiratory muscle training] results in marked improvement in inspiratory muscle strength, as well as improvement in functional capacity, ventilatory response to exercise, recovery oxygen uptake kinetics, and quality of life.

Winkelmann ER, Chiappa GR, Lima CO, Viecili PR, Stein R, Ribeiro JP.
Addition of inspiratory muscle training to aerobic training improves cardiorespiratory responses to exercise in patients with heart failure and inspiratory muscle weakness.
Am Heart J. 2009 Nov;158(5):768.e1-7. Epub 2009 Oct 2.
Hospital de Clinicas de Porto Alegre, RS, Brazil.
… CONCLUSION: This randomized trial demonstrates that the addition of IMT [inspiratory muscle training] to AE [aerobic exercise training] results in improvement in cardiorespiratory responses to exercise in selected patients with CHF and IMW [inspiratory muscle weakness]. The clinical significance of these findings should be addressed by larger randomized trials.

Mancini DM, Henson D, La Manca J, Donchez L, Levine S.
Benefit of selective respiratory muscle training on exercise capacity in patients with chronic congestive heart failure.
Circulation. 1995 Jan 15;91(2):320-9.
Cardiovascular and Pulmonary Sections, Philadelphia Veterans Administration Medical Center, Pa.
… CONCLUSIONS: Selective respiratory muscle training improves respiratory muscle endurance and strength, with an enhancement of submaximal and maximal exercise capacity in patients with heart failure. Dyspnea during activities of daily living was subjectively improved in the majority of trained patients.

Cystic Fibrosis
de Jong W, van Aalderen WM, Kraan J, Koëter GH, van der Schans CP.
Inspiratory muscle training in patients with cystic fibrosis.
Respir Med. 2001 Jan;95(1):31-6.
Department of Rehabilitation, University Hospital Groningen, The Netherlands.
… After training no significant differences were found in changes from baseline in pulmonary function, exercise capacity, dyspnoea and fatigue. It is concluded that low-intensity inspiratory-threshold loading at 40% of Pimax [maximal static inspiratory pressure] was sufficient to elicit an increased inspiratory-muscle endurance in patients with CF.

Reid WD, Geddes EL, O’Brien K, Brooks D, Crowe J.
Effects of inspiratory muscle training in cystic fibrosis: a systematic review.
Clin Rehabil. 2008 Oct-Nov;22(10-11):1003-13.
Department of Physical Therapy, University of British Columbia, Muscle Biophysics Laboratory, Vancouver, BC, Canada.
…CONCLUSION: The benefit of IMT [inspiratory muscle training] in adolescents and adults with cystic fibrosis for outcomes of inspiratory muscle function is supported by weak evidence. Its impact on exercise capacity, dyspnoea and quality of life is not clear. Future research should investigate the characteristics of the subgroup of people with cystic fibrosis that might benefit most from IMT.

Enright S, Chatham K, Ionescu AA, Unnithan VB, Shale DJ.
Inspiratory muscle training improves lung function and exercise capacity in adults with cystic fibrosis.
Chest. 2004 Aug;126(2):405-11.
School of Health Care Professions, University of Salford, Manchester, UK.
… CONCLUSION: An 8-week program of high-intensity IMT [inspiratory muscle training] resulted in significant benefits for CF patients, which included increased IMF and thickness of the diaphragm (during contraction), improved lung volumes, increased PWC, and improved psychosocial status.

Diabetes
I Corrêa AP, Ribeiro JP, Balzan FM, Mundstock L, Ferlin EL, Moraes RS.
Inspiratory muscle training in type 2 diabetes with inspiratory muscle weakness.
Med Sci Sports Exerc. 2010 Dec 21.
Exercise Pathophysiology Research Laboratory and Cardiovascular Division, Hospital de Clínicas de Porto Alegre. Rua Ramiro Barcelos 2350, 90035-007, Porto Alegre, RS, Brazil 2Department of Medicine, Faculty of Medicine, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
CONCLUSIONS: Patients with type 2 diabetes may frequently present inspiratory muscle weakness. In these patients, IMT [inspiratory muscle training] improves inspiratory muscle function with no consequences in functional capacity or autonomic modulation.

Muscle oxygenation and blood flow
Clark A, Coats A.
Mechanisms of exercise intolerance in cardiac failure: abnormalities of skeletal muscle and pulmonary function.
Curr Opin Cardiol. 1994 May;9(3):305-14.
Department of Cardiac Medicine, National Heart and Lung Institute, London, United Kingdom.
The syndrome of chronic heart failure is characterized by exercise intolerance. Exercise is limited by shortness of breath and fatigue, and either symptom occurs in the same patient depending on the type of exercise performed. Exercise capacity correlates poorly with indices of central hemodynamic function, but the increased ventilatory response in chronic heart failure correlates well with exercise capacity. Possible pulmonary causes have been explored, including increased dead space ventilation, abnormal airway function, and abnormal diffusion capacity. However, the finding of hypocapnia and hyperoxemia in arterial blood during exercise in patients with heart failure suggests that blood gas values reflect hyperventilation, and that any abnormality of pulmonary function is secondary to changes elsewhere. Skeletal muscle is abnormal in chronic heart failure, and shows changes in structure, bulk, exercise capacity, blood flow, and intrinsic metabolic activity…

Gustafsson U, Sjöberg F, Lewis DH, Thorborg P.
The effect of hypocapnia on skeletal muscle microcirculatory blood flow, oxygenation and pH.
Int J Microcirc Clin Exp. 1993 Apr;12(2):131-41.
Clinical Research Center, Faculty of Health Sciences, University Hospital, Linköping, Sweden.
Hypocapnia is known to decrease blood flow and tissue oxygen tension in the brain and the splanchnic organs, but there are few and contradictory results in skeletal muscle. The aim of the present study was to investigate the effect of hypocapnia on microcirculatory blood flow, local skeletal muscle PO2 (PtO2) and pH (pHt)… These results show that hypocapnia induces a 20% decrease in LDF [laser-Doppler flowmetry] flow and a 9% reduction in PtO2 with an unchanged pHt level. In this skeletal muscle model, the decrease in microcirculatory blood flow due to vasoconstriction leads to a reduction in both tissue oxygenation and in the removal of acid metabolites, which counteract a developing tissue alkalosis.

Thorborg P, Jorfeldt L, Löfström JB, Lund N.
Striated muscle tissue oxygenation and lactate levels during normo-, hyper- and hypocapnia. A study in the rabbit.
Microcirc Endothelium Lymphatics. 1988 Jun;4(3):205-29.
Department of Anesthesiology, University Hospital, Linköping, Sweden.
The relationship between striated muscle tissue oxygenation during hyper- and hypocapnia, and lactate levels and venous pO2 (pvO2) was studied in a rabbit model… A decrease in pvO2 was seen during hypocapnia… In this study, hypercapnia influenced striated muscle tissue oxygenation only to a minor degree while hypocapnia influenced it more but not as much as expected…

Laffey JG & Kavanagh BP
Hypocapnia
New England Journal of Medicine 2002, 347(1) 43-53.
Section “Neurologic Effects of Hypocapnia”
Because both hypocapnia and alkalosis cause a leftward shift of the oxyhemoglobin dissociation curve, off-loading of oxygen at the tissue level is restricted. In addition, hypocapnia causes systemic arterial vasoconstriction, decreasing the global and regional oxygen supply and compounding the reduction in the delivery of oxygen to tissue.

Nunn JF. Applied respiratory physiology , 1987, 3rd ed. London: Butterworths.

Foëx P, Ryder WA
Effect of CO2 on the systemic and coronary circulations and on coronary sinus blood gas tensions, Bulletin of European Physiopathology and Respirology
1979 Jul-Aug; 15(4): p.625-638.

Karlsson T, Stjernström EL, Stjernström H, Norlén K, Wiklund L
Central and regional blood flow during hyperventilation. An experimental study in the pig
Acta Anaesthesiol Scand. 1994 Feb; 38(2): p.180-186.

Okazaki K, Okutsu Y, Fukunaga A
Effect of carbon dioxide (hypocapnia and hypercapnia) on tissue blood flow and oxygenation of liver, kidneys and skeletal muscle in the dog
Masui, 1989 Apr, 38 (4): p. 457-464.

Wexels JC, Myhre ES, Mjøs OD
Effects of carbon dioxide and pH on myocardial blood-flow and metabolism in the dog
Clin Physiol. 1985 Dec; 5(6): p.575-588.

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